Furnace issue

[gorphus]

My thermostat is not on. I checked and it doesn't operate on batteries, so it should be on line voltage. I don't have a voltmeter, so I can't check the power coming in. We have 2 electrical boxes and I have reset all the breakers to no avail. Every other outlet / light source we use is working. There were no breakers labelled "furnace" or "attic."

There is a fuse at outlet where the furnace plugs in that looks ok and it shouldn't have switched off, but I'll double check that today. It screws into one side of the electrical box and there is a 3-prong outlet on the other half of the box where the furnace is plugged into. Our power was switched off at some point, but that shouldn't have caused a surge that burned the fuse, should it?

We just bought the place, so I'm still sorting out where everything is. Is there a chance there is another electrical box in the crawl space? Seems unlikely since the furnace is in the attic and the A/C is outside.

Thanks in advance for any help.

 

[user 4883]

Unless it is a glass fuse, I'm not sure how you determined the fuse to be good without a volt meter.
If I could have only one tool to troubleshoot and HVAC system, it would be a volt meter.
Furnaces are typically on a dedicated circuit and do not plug into an outlet.
I suspect your looking at the condensate pump cord/plug.
Furnaces in attics are subject to rodents chewing on electrical wires.
Can you remove the panel on the furnace, hold down the safety switch and see if there are any indicator lights lit up on the furnace circuit board?
On the thermostat wires on the wall after removing the thermostat, if you jumper (R) red and (W) white, does the unit fire up?

 

[JoeD]

Could the furnace be turned off at the disconnect that should be near the furnace?

 

[gorphus]

It is an American Standard 80 single stage furnace. Didn't write down the model number.

I'll check to see what happens if I jump the red and white at the thermostat.

There is a light bulb socket that feeds off the same line as the (potential) condensate pump cord/plug which doesn't get power. The two switches nearest those lines (in the hallway in the attic below) are both switched on.

One complication: if the gas is shut off, will the furnace shut down as well? My wife informed me that we didn't switch our PG&E over when we moved. We used the gas stove this morning, so it could still be on; the stove could have worked off residual gas in the line as well, I suppose.

I couldn't find a disconnect near the furnace. There is a power switch for the pilot light inside one of the panels (on/off) which I cycled a few times. After replacing the panels, no change. I made sure the panels went on properly to depress the door interlock, so that shouldn't be the problem.

I think I have to call in an electrician / serviceman to get this sorted out. Too many unknowns at this point. Fortunately, we live in CA, so the temperature at night isn't too bad.

 

[gorphus]

Anyone have an idea where the circuit breaker for the furnace would be? It is not listed on either of the two panels (one inside, one outside), which list everything else (dryer, hallways, bathroom, kitchen, etc.). Some web sites suggest that it would be in the attic near the furnace, but I don't recall seeing anything. It has to connect to the main house power somewhere . . .

 

[nealtw]

It will be in one of those panels, if there are no lights on the furnace, you will need some kind of test light to see if you have power there and then you can flip breakers until you find it.
There is usually a switch in the hallway for the furnace it will be higher on the wall than all the other switches. I have seen where that switch has failed.

 

[JoeD]

There could/should be a disconnect switch near the furnace. That won't be the circuit breaker. There will also be a circuit breaker in one of those panels for it.

 

[user 4883]

Another possibility could be that the float in the condensate box is stuck and this will kill power to the furnace.
Open the box and check the float.

 

[gorphus]

Thanks everyone for the input. I made a service call. Turns out the breaker wouldn't reset, but it clicked into place like all the other ones did. Also, whoever did it put that circuit on a 15A breaker. The furnace pulls 11+ when it is on, the furnace blower pulls ~4A and there is a light switch on it as well. So, setup for failure.

Still need to invest in a voltmeter.

 

[nealtw]

The light switch is there by code and don't change the breaker size unless you change the wire to. Glad you got it fixed to bad you had to buy the help.